linux-kernel - [PATCH V5 5/8] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

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Message-Id: <20230810160412.820246-6-ltykernel@gmail.com>
Date:   Thu, 10 Aug 2023 12:04:08 -0400
From:   Tianyu Lan <ltykernel@...il.com>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, daniel.lezcano@...aro.org, arnd@...db.de,
        michael.h.kelley@...rosoft.com
Cc:     Tianyu Lan <tiala@...rosoft.com>, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com
Subject: [PATCH V5 5/8] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

From: Tianyu Lan <tiala@...rosoft.com>

In sev-snp enlightened guest, Hyper-V hypercall needs
to use vmmcall to trigger vmexit and notify hypervisor
to handle hypercall request.

Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
---
 arch/x86/include/asm/mshyperv.h | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 9f11f0495950..07cad6c2af56 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -62,12 +62,12 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
 	if (!hv_hypercall_pg)
 		return U64_MAX;
 
-	__asm__ __volatile__("mov %4, %%r8\n"
-			     CALL_NOSPEC
+	__asm__ __volatile__("mov %[output], %%r8\n"
+			     ALTERNATIVE(CALL_NOSPEC, "vmmcall", X86_FEATURE_SEV_ES)
 			     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
-			       "+c" (control), "+d" (input_address)
-			     :  "r" (output_address),
-				THUNK_TARGET(hv_hypercall_pg)
+			     "+c" (control), "+d" (input_address)
+			     : [output] "r" (output_address),
+			       THUNK_TARGET(hv_hypercall_pg)
 			     : "cc", "memory", "r8", "r9", "r10", "r11");
 #else
 	u32 input_address_hi = upper_32_bits(input_address);
@@ -103,7 +103,8 @@ static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
 
 #ifdef CONFIG_X86_64
 	{
-		__asm__ __volatile__(CALL_NOSPEC
+		__asm__ __volatile__("mov %[thunk_target], %%r8\n"
+				     ALTERNATIVE(CALL_NOSPEC, "vmmcall", X86_FEATURE_SEV_ES)
 				     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
 				       "+c" (control), "+d" (input1)
 				     : THUNK_TARGET(hv_hypercall_pg)
@@ -148,13 +149,13 @@ static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
 
 #ifdef CONFIG_X86_64
 	{
-		__asm__ __volatile__("mov %4, %%r8\n"
-				     CALL_NOSPEC
-				     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
-				       "+c" (control), "+d" (input1)
-				     : "r" (input2),
-				       THUNK_TARGET(hv_hypercall_pg)
-				     : "cc", "r8", "r9", "r10", "r11");
+		__asm__ __volatile__("mov %[output], %%r8\n"
+		     ALTERNATIVE(CALL_NOSPEC, "vmmcall", X86_FEATURE_SEV_ES)
+		     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+		       "+c" (control), "+d" (input1)
+		     : [output] "r" (input2),
+		       THUNK_TARGET(hv_hypercall_pg)
+		     : "cc", "r8", "r9", "r10", "r11");
 	}
 #else
 	{
-- 
2.25.1